U.S. Pat. No. 6,756,139 described a coated conductor architecture based on IBAD-MgO, which comprises four or five separately deposited layers between the metal substrate and the superconducting layer. Among the described structures are included: (1) a structure including a substrate/a layer of Al2O3/a layer of Y2O3/a layer of IBAD-MgO/a homoepitaxial layer of MgO/a layer of SrRuO3/a layer of YBCO; and (2) a structure including a substrate/a layer of Er2O3/a layer of IBAD-MgO/a homoepitaxial layer of MgO/a layer of SrRuO3/a layer of YBCO.
Excellent critical current density values have been achieved using either of these architectures, but among the various intermediate layers, the homoepitaxial layer of MgO can present the most difficulties. First, the deposition rate is slow, requiring long deposition times and affecting the potential cost of production. Also, this layer is soft and hygroscopic, necessitating special care following deposition to avoid damage that would interfere with subsequent growth of the YBCO layer.
Due to these problems, elimination and/or replacement of this layer has remained a goal of researchers.
Do et al. (U.S. Pat. No. 6,190,752) describe TiN as one exemplary material with a rock salt like structure among other materials including magnesium oxide, such materials suitable as a thin film upon a smooth amorphous surface of a metal alloy substrate.
Kim et al., Physica C, v. 377, pp. 227-234 (2002) describe: (a) a structure of epitaxial TiN on a single-crystal (001) magnesium oxide substrate; and, (b) a structure of epitaxial TiN on a cerium oxide intermediate layer on a single-crystal (001) magnesium oxide substrate. They indicated that the cerium oxide intermediate layer was necessary (comparing (a) and (b)) to avoid a significant drop in Tc and Jc by a subsequently deposited YBCO layer, such YBCO layer deposited at between 700-800° C., on each structure.
Recently, Huhne et al., Appl. Phys. Lett., v. 65, no. 14, pp. 2744-2746 (2004) describe the deposition of TiN films using ion beam assisted deposition on amorphous substrates of Si/Si3N4 substrates.
Despite the appearance of TiN within various superconducting structures, additional development using TiN as a layer within a superconducting structure has now been explored.